Time synchronization for DFC77 devices using sound speakers.
This program generates a time DFC77 signal and sends it to the speakers. By placing any DFC77 device near the speaker it should be synchronized within a few minutes.
Clearly, the funcionality depends on the sound card capabilities, which should have support for the sample rate of 192kHz, the distance between the speaker and the DFC77 device, and the lack of any interference. Place your speaker and device far from electronic devices such as TVs, monitors, computers, etc.
To test the script with audible modulation change the frequency to something reasonable, e.g.:
python dfc77-sync.py -f 440
You can also play though a different device. Just experiment with options -l and -d.
Usage:
usage: dfc77-sync.py [-h] [-l] [-d DEVICE] [-f FREQUENCY] [-a AMPLITUDE] [-s SAMPLERATE] [-u]
Synchronizes DFC77 devices using sound speakers.
optional arguments:
-h, --help show this help message and exit
-l, --list-devices show list of audio devices and exit
-d DEVICE, --device DEVICE
output device (numeric ID or substring)
-f FREQUENCY, --frequency FREQUENCY
frequency in Hz (default: 77500 Hz)
-a AMPLITUDE, --amplitude AMPLITUDE
amplitude (default: 1)
-s SAMPLERATE, --samplerate SAMPLERATE
sample rate (default: 192000)
-u, --utc set time in UTC
Requirements:
- sounddevices: https://pypi.org/project/sounddevice/
The code is inspired by and based on:
- "How to manipulate a radio controlled clock via speaker" by Bastian Born: https://bastianborn.de/radio-clock-hack
- txtempus by Henner Zeller: https://github.com/hzeller/txtempus/
- DFC77 technical desciption: https://en.wikipedia.org/wiki/DCF77